The present invention is related to a starter apparatus for an internal combustion engine.
A starter apparatus for an internal combustion engine is known including a starter motor provided with a drive shaft; an axially shiftable starting gear engageable with the ring gear of the internal combustion engine; a drive train for transferring rotary motion of the drive shaft of the starter motor to the starting gear, the drive train having a torsional rigidity and including a plurality of parts from the starting gear to the drive shaft; a free wheel clutch coupled with the drive shaft; and a shock absorbing means for damping torque shocks between the starting gear and the drive shaft occurring on rotation of the drive shaft.
A starting device, the so-called starter of the internal combustion engine, including means for damping the compression and decompression impacts in the starter mechanism is described in U.S. Pat. No. 4,561,316. This starter has a hollow gear in a planetary gear device used as a transmission gear unit in the starter which has shock damping means in the form of a rubber pad in its housing. A free wheel clutch is used for mechanical decoupling of the starter motor and the internal combustion engine, when the engine is running and has been accelerated by the starter rotation. The periodic release and engagement of the free wheel clutch because of the piston motion in the cylinders of the internal combustion engine due to its gas torque moment is an undesirable side effect in the so-called full rotation stage, in which the internal combustion engine has been put into rotation by the starter mechanism without accelerated combustion. This periodic release and engagement of the free wheel clutch depends on the moment of inertia values of the starter and the engine acting on the gear shaft and the drive torque of the starter and on the load on the crank shaft of the internal combustion engine. Fundamentally the released phase of the free wheel clutch is longer on starting with a transmission gear unit by which the starting moment of inertia is increased than on starting without it. A longer released phase results also at higher temperatures, since then the crankshaft friction moment is reduced, while the gas torque moment of the internal combustion engine increases.
When rotational play is present in the drive train of the starter having a starting gear, the starter mechanism exhausts this rotational play during each load change on engagement of the free wheel clutch and, because of that, a shock or impact is expected on the sides of the starting gear. These impacts on the gear teeth depend on the incorrect inertial moments of the starter and the crank shaft, on the total rotational play, on the rigidity of the starter drive train, on the differences in angular speed between the ring gear of the internal combustion engine and the starting gear as well as on the drive and load on the starting gear.
The known elastic support of the hollow gear in the starter housing with a rubber cushion or with a polygonal shaped rubber body between the hollow gear and the housing wall according to European Patent Document 0 375 396 A1 is not satisfactory at least in starter mechanisms of the larger and medium size starters, since this type of damping rubber has a strongly progressive characteristic curve and thus already is much too hard during a minimal deformation. The same goes for the starter described in U.S. Pat. No. 5,127,279, in which the drive shaft of the transmission gear unit connected with the starting gear is connected with a hollow gear by an elastic connecting means made from rubber or the like for damping the torque impacts or shocks occurring in the drive train during the starting process. Furthermore these damping elements would be destroyed in the course of time in the starter apparatus of larger and medium size by the comparatively very high shocks or impacts acting on them. Starter devices of comparatively higher power predominantly are equipped without transmission gear units because of these high shock loads. Because of that, a correspondingly larger expensive starter motor must be used and the impact loads must be received by the free wheel clutch responding in a pulsating manner, whereby also a loud noise is generated.